1. Field of the Disclosure
The present invention relates to an electrophotographic imaging apparatus, and more particularly to a backup belt assembly for use in a fusing system of such an apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus, such as a printer or copier, a latent image is formed on a light sensitive drum and developed with toner. The toner image is then transferred onto media, such as a sheet of paper, and is subsequently passed through a fuser assembly where heat and pressure are applied to melt and adhere the unfused toner to the surface of the media. There is an assortment of devices available to apply heat and pressure to the media sheet, such as radiant fusing, convection fusing, and contact fusing. Contact fusing is the typical approach of choice for a variety of reasons including cost, speed and reliability. Contact fusing systems themselves can be implemented in a variety of ways. For example, a hot roller fusing system includes a fuser roller and a backup roller in contact with one another so as to form a nip therebetween, which is under a specified pressure. A heat source is associated with the fuser roll, backup roll, or both rollers in order to raise the temperature of the rollers to a temperature capable of adhering unfixed toner to a medium. As the medium passes through the nip, the toner is adhered to the medium via the pressure between the rollers and the heat resident in the fusing region (nip). As speed requirements demanded from fusing systems are increased, the size of the fuser and backup rollers must be increased, and the capability of the heat source must be expanded to sustain a sufficient level of energy necessary to adhere the toner to the medium in compensation for the shorter amount of time that the medium is in the nip. This in turn can lead to higher cost, and large rollers.
As an alternative to the above described hot roller fusing system, a backup belt fusing system can be used. In such backup belt fusing systems, there is typically a stationary pressure pad against which the fuser roller is pressed through a belt to form a fusing nip therebetween. A heat source is then applied to the fuser roll, belt or both to generate sufficient heat within the system to adhere unfixed toner to a medium as the medium is passed between the fuser roller and the belt. Generally, a backup belt fusing system has a quicker warm up time with respect to a comparable fusing system employing a backup roller. Also, a backup belt fusing system allows reduction in the size of the fusing system necessary to attain the adhesion of toner to media, which in turn reduces the cost of the fusing system. However, although generally successful in achieving a larger nip width, the typical backup belt fusing system has drawbacks. The backup belt is vulnerable to wear due to its inner surface repeatedly slidingly contacting the pressure pad. The contacting surfaces of the backup belt and the pressure pad abrade each other which, after a long period of operation, may potentially result in belt failure. In addition to wear issues, the torque required to drive the fuser roller is substantially increased, due to the contact with the pressure pad, which can damage the gear train driving the fixing members due to increased stress during rotation.
Accordingly, alternative designs of fuser systems including backup belt fusing systems are desired.